Well, who's asking? Polls have own dynamics

So the state Republican Party comes out with this poll Thursday that says the presidential race in Pennsylvania is virtually tied when every other poll lately has Democratic President Barack Obama up 9 or 11 points.

You gotta love polls, right?

First, maybe the Republican poll is right. Maybe Mr. Obama had the support of 48 percent of likely Pennsylvania voters and Republican nominee Mitt Romney had 47 percent. Maybe the race did tighten, though it's hard to see how it would have gone from the president's 11-point lead in a Philadelphia Inquirer poll between Sept. 9 and 12 to 1 point last weekend.

The Republican Party poll by Susquehanna Polling & Research was conducted last Saturday, Sunday and Monday before publication of Mr. Romney's May statement to top donors that 47 percent of Americans, who get some kind of government aid, see themselves as victims.

Second, maybe the Republican poll is an outlier. When you have a lot of polls, sometimes one comes up with strange results. Of the four polls right before this one - one overlapping on two days with the Susquehanna poll - three had Mr. Obama up 9 points and the other 11 points.

Or maybe - and this is likelier - different methods of sampling voters produced the differences.

The Susquehanna poll surveyed 800 likely voters and had a margin of error of plus or minus 3.46 percentage points.

An effort to reach Susquehanna President James Lee on Friday was unsuccessful, but let's give the company the benefit of the doubt and assume its poll was on the up and up. Here are a few possibilities for the differences, courtesy of Berwood Yost, Ph.D., director of the Floyd Institute for Public Policy at Franklin & Marshall College. Full disclosure: F&M routinely polls on behalf of The Times-Tribune and other news outlets statewide.

So it might be that Susquehanna called on too many Republicans and too few independents, who, according to previous polls, are backing Mr. Obama in Pennsylvania. A recent Allentown Morning Call poll that had Mr. Obama up 9 points used 49 percent Democrats, 40 percent Republicans and 11 percent independents/other parties and still showed Mr. Obama up 9 points.

- The Republicans polled only people who said their chances of voting were excellent or good. This could skew toward Republicans, who are likelier to vote anyway, Dr. Yost said. It's hard to believe this was a factor, though, because the Morning Call polls used only people who were definitely or very likely to vote, which is pretty close to what the Republicans did.

- The Republicans sampled only people who voted in one of the last four general elections, 2008 through 2011, and new voters who registered since last November. None of the other polls surveyed that way.

The Morning Call used people who voted in at least one of the last eight general or primary elections or registered to vote since 2009. That universe is larger.

But maybe the poll was right for another reason: margin of error. Each figure could be off by 3.46 percent.

For our purposes, let's round that to 3.5 points.

That means each percentage could be that much higher or lower just because of sampling error.

Add 3.5 points to Mr. Obama's percentage, you get 51.5 percent. Take that much away from Mr. Romney and you get 43.5 percent. That's an 8-point margin, or about what the other polls were showing.

This kind of error creeping in is statistically rare, but it can happen.

The ultimate way to tell is what happens in the next few polls.

If they show Mr. Obama with a big lead, you'll know the Republican poll was an exception. If the next few show a much tighter race, you'll know the Republicans were on to something.

One other way to tell: if Mr. Romney or Republican groups start advertising on television in Pennsylvania again. In a 1-point state, they'll definitely be back. If Mr. Obama stays up by 9 points or more, they won't.

If the Romney/Republican groups stay away, don't be surprised if the state Republican Party advertises against Mr. Obama on its own. The party put out a fundraising appeal almost immediately after releasing its Obama-by-1-point poll.

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